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[linux-dvb] Re: timing in dvb-kernel
On Monday 24 November 2003 15:28, Jeremy Hall wrote:
> Per some suggestions, I opted to try the dvb-kernel tree, but found that
> timing is worse in the dvb-kernel.
>
> I have requirements to be able to change voltage from h to v in under 8ms
> consistently, and can successfully achieve this with the DVB code, but
> dvb-kernel seems not able to do this. Do you have suggestions on what I
> might try to improve the latency?
This requires two modifications:
[1] I committed a change to 'dvb-kernel' which increases speed of the
I2C bus for *full-featured* cards to 275 kHz (same value as in DVB).
Please update file av7110.c from dvb-kernel CVS.
[2] Apply the following patch to saa7146_i2c.c:
----------------- snip ----------------------------
diff -p -u -r1.26 saa7146_i2c.c
--- saa7146_i2c.c 14 Nov 2003 11:42:04 -0000 1.26
+++ saa7146_i2c.c 25 Nov 2003 03:29:29 -0000
@@ -301,7 +301,7 @@ int saa7146_i2c_transfer(struct saa7146_
goto out;
}
- if (count > 3) short_delay = 1;
+ short_delay = 1; // OE test
do {
/* reset the i2c-device if necessary */
----------------- snip ----------------------------
Note that without [2] modification [1] is almost useless,
because each I2C access causes a delay of 10..20ms.
I suggested several times to improve this but I was ignored...
Oliver
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